1. Field of the Invention
The present invention relates to a method for fabricating a polymeric optic waveguide grating, and more particularly, to a method for fabricating a polymeric optic waveguide grating using an imprint lithography process.
2. Description of the Related Art
Recently, as data traffic is rapidly increased, demand and concern on the optic communication are increased, so that expectation and role on a total system and respective optic communication parts constituting the total system are also of great importance.
Together with this, a research on a new optic device capable of securing a low price and a high reliability as well as a high performance is also being performed in various ways.
Due to this tendency, as interests on a polymeric optic device and a liquid crystal optic device as well as a silica optic device are also increased, these devices reach a phase that common-use products appear.
Specifically, as a wavelength division multiplexing (WDM) communication is generalized, a demand on an add/drop multiplexer, a planar waveguide wavelength filter, or the like using Fiber Bragg Grating tends to rapidly increase. In particular, since the polymeric optic devices can be massively fabricated by a simple process, many developments are made in fields of an optic waveguide device and grating.
According to such a demand, the optic waveguide grating having a cyclic refractive index varying region (grating region) formed in an optic axis direction of an optic waveguide is considered for a variety of applications such as an optic filter, or the like in the optic communication system. Among them, a grating period having a relatively long period above a few hundreds μm is called a long period grating. The long period grating is expected to be used in a gain equalizer, a band stop filter, or the like.
The long periodic optic waveguide grating is known to have a characteristic varied depending on temperature variation. An analysis on the temperature characteristic of the optic waveguide grating is being performed.
In other words, the optic waveguide grating uses SiO2 as a main component of the optic waveguide to form a core region serving as a light propagation region of the optic waveguide. Further, in order to form the grating region by periodically modulating the refractive index in the core region, GeO2 is generally added. At this time, comparing to the temperature-dependent refractive index variation of SiO2, the temperature-dependent refractive index variation of GeO2 is more greatly generated. Thus, temperature-dependencies of the refractive indexes in the core region and a clad region around the core region are shown different from each other. As a result, the long periodic waveguide grating formed in the optic waveguide has a different temperature-dependency of an effective refractive index in each of a core propagation light and a clad mode light, so that if the temperature is varied, the operation wavelength is also varied.
On the other hand, the temperature-dependency of the refractive index in each of SiO2 glass, GeO2 glass and B2O3 glass is known. On basis of this, a technique is known in which, in case the optic waveguide is formed of a quartz-based optic fiber, Germanium (Ge) and Boron (B) are added together to the core region to reduce the temperature-dependency in the characteristic of the optic waveguide grating.
Until now, a conventional fabrication method of the above device is performed by an etching using a photolithography process. However, since the conventional fabrication method has a limit in the resolution of the photolithography process and is performed through several steps, much time and cost is needed.
As another conventional method proposed, an electron-beam writing method is proposed, but has a disadvantage in that much time is needed.
Accordingly, a new fabrication method is required for realizing a massive fabrication at a low price through a relative simple process.